Preparation and structure of manganese molybdates
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Manganese molybdates were prepared by precipitation in aqueous solution. Several monohydrates were obtained in the pH range 3-8. A yellow precipitate that formed initially is also a monohydrate but transforms at 60-100 °C into other, more crystalline, products depending upon pH. The compound obtained at pH 7-8 is triclinic, with a = 5.776 (4) Å, b = 5.964 (4) Å, c = 6.992 (4) Å, α = 100.32 (5)°, β = 95.56 (5)°, γ = 106.81 (5)°, and Z = 2. The structure consists of molybdate tetrahedra and Mn(II) octahedra in which the tetrahedra share four corners with four different octahedra. The water molecule is coordinated to the manganese. Heating any of the hydrates to elevated temperatures converts them to the α-MnMoO4 phase. In contrast, hydrothermal treatment of the hydrates at 200 °C transforms them to an anhydrous product with the NiWO4 structure. A compound, Na2Mn2(MoO4)3-3H2O, was prepared from alkaline solution. Hydrothermal treatment at 200 °C converted it to NaMn2(O-H)(H2O)(MoO4)2. The structure of this latter phase confirmed the bridging scheme proposed earlier, as it was possible to locate the positions of the hydrogen atoms. © 1985, American Chemical Society. All rights reserved.
author list (cited authors)
Clearfield, A., Moini, A., & Rudolf, P. R.